Commercialization of bioleaching for base-metal extraction

This paper is a progress report on the commercialization of using bioleachi ng for base-metal concentrates. The paper focuses on bioleach processes for recovering copper from chalcopyrite and nickel/cobalt from pentlandite/pyr rhotite. Data is discussed from pilot-plant trials in which an overall reco very >95% was obtained for the bioleaching of copper from chalcopyrite. The pilot plant was operated in closed circuit with solvent extraction and ele ctrowinning circuits for final metal recovery. For the bioleaching of nicke l and cobalt from pentlandite/pyrrhotite, an overall recovery of 97% was ac hieved. Precipitation routines were used to produce a final nickel/cobalt p roduct. The pilot plants were capable of treating a few kilograms of concen trate per day. Prominent features in the design of a 1-t/day (1.1-stpd) cop per-bioleach demonstration plant for the treatment of chalcopyrite concentr ate are discussed The plant, which is now under design, will be constructed and operated based on the results obtained from the laboratory pilot-plant campaigns. Issues of scale-up for the demonstration plant, together with i ntegration into upstream and downstream processing, aia also addressed. Ind ependently derived capital and operating costs are presented for a possible commercial plant. These cost studies indicate the principle economic issue s in considering the application of bioleaching to the extraction of base m etals. The benefits of bioleaching complex concentrates that are not amenab le to physical beneficiation and economic treatment by conventional smeltin g are highlighted Issues, such as the environmental aspects, that illustrat e the benefits of bioleach technology are given.